<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app" class="d-flex container">后盾人</div>
    <script>
        //使用style对象可以对样式属性单独设置，使用cssText可以批量设置行样式
      let app = document.getElementById('app')
      app.style.backgroundColor = 'red'
      app.style.color = 'yellow'

      //批量设置style
    //   app.style.cssText = `background-color:red;color:yellow`


    //通过属性setAttribute来设置
    //  app.setAttribute('style', `background-color:red;color:yellow;`)
    </script>
</body>
</html>